Electric heater



Oct. 8, 1929. c. c. ABBOTT ET AL 1,731,119

ELECTRIC HEATER Filed July 15. 1925 v I J I 'Will/IIIIIIII/III7III/IfiI/IIIII Tm/enCors Charles C. Abbott,

:Arflw w E. H u mt, y Their- ACCorney.

Patented Oct. 8, 1929 UNITED STATES PATENT OFFICE CHARLES C. ABBOTT AND ARTHUR E. HUNT, OF PITTSFIELD, MASSACHUSETTS, ASSIGNORS TO GENERAL ELECTRIO COMPANY, A CORPORATION OF NEW YORK ELECTRIC HEATER Application filed July 15,

Our invention relates to electric heaters, more particularly to electric heaters of the sheathed wire type, and has for its object an electric heater of a simple and rugged construction.

More particularly our invention relates to heaters of the sheathed wire type. Such heaters consist, briefly, of a resistance conductor which is embedded in a mass of insulating material in a metallic sheath.

Ordinarily, the resistance Conductor extends throughout the length of the sheath with a terminal projecting from each end of the sheath. This arrangement of the terminals is particularly applicable to heaters of this type, especially to the smaller sizes.

n carrying out our invention in one form we place a plurality of sheathed wire heating units lengthwise inside a sheath and then compact the two units in the sheath. The

two units are then connected together at one end and this end of the sheath is sealed, while the other two ends of the units are providedwith terminals which project from the opposite end of the sheath.

For a more complete understanding of our invention reference should be had to the accompanying drawing in which Fig. 1 is a view mainly in section of an electric heater em bodying our invention; Fig. .2 is a sectional view along the line 22 of Fig. 1 looking 1n the direction of the arrows; Fig. 3 is 9. Ian view of a partially completed heater; Fig. 4 is a sectional view along the line H of Fig. 3 looking in the direction of the arrows; Fig.

5 is a view showing the heater in a more advanced stage of its construction; Fig. 6 is an end elevation view of Fig. 5; Fig. 7 is a fragmentary view partly in section showing a detail of construction; while Fig. 8 is a sectional view of a modified form of our invention.

Referring to the drawing, the electric heater in one form of our invention comprises an outer metallic sheath 10 in which is secured a plurality of sheathed wire heating units, two units 11 and 12 being shown. The sheathed wire units 11 and 12 may be, and are shown, of the helical coil type described and 0 claimed in Patent No. 1,367,341 to Abbott 1925. Serial No. 43,858.

dated February 1, 1921, each being provided with an outer metallic sheath 13 in which a helical resistance conductor 14 is held central by means of powdered insulating material 15 which is compacted to a hard dense mass by reducing the diameter of the. sheath by rolling or swaging. In order to obtain an intimate thermal relation between the heating units and the sheath 10, the sheath 10 is reduced in diameter after the heating units have been inserted therein whereby the sheath is compacted tightly on the heating units, and the heating units are pressed together and caused to assume such complementary shapes as to substantially fill the sheath. As shown in Fig. 2 the reduction in diameter of the sheath 10 causes the heating units 11 and 12 to assume a circular crosssection, each unit being substantially semicircular in cross-section. A brazed joint 16 is made between the resistance conductor 14 of the heating units at one end, and this end of the sheath 10 is sealed by means of a cap 17 which is brazed at 18 to the end of the sheath 10. The opposite or outer ends of the heating units projectfrom the sheath 10, and are provided with terminals 19 and 20 whereby the heater may be connected to a suitable electrical source of supply.

In the construction of the heater the sheath 10, which is provided with counterbores 10* and 10 at its nds, is first flattened somewhat, as indicated in Fig. 4, to allow the heating units 11 and 12 to be freely inserted lengthwise therein. It will be understood that the heating units are provided with the terminals 19 and 20 at one end only, no terminals being provided for the other or inner ends. The ends of the heating units project from each end of the sheath for a substantial distance. After the heating units have been thus assembled in the sheath, the sheathis compacted by rolling or swaging, and thereby caused to assume a circular cross-section, this compacting operation being carried out until the heating units are pressed together as previously described in connection with Fig. 2. The sheaths 13 of the heating units are now cut away at their inner ends near the end of the sheath 10 so of adhesive tape 28.

as to expose the ends of the resistance conductors which are then twisted together and further secured by the brazed joint 16.

The sheath 10 is also cut back for a short distance at the end adjacent the joint 16' to remove the counterbore 10", this end being beveled. The object of the counterbores in the ends of the sheath is to prevent reduction to a large extent of the ends of the heating unit lying in the counterbores whereby greater electrical clearance is obtained. This is illustrated in Figs. 6 and'7. While the portions of the heating units in the counter-' bores may be reduced or flattened somewhat they are not flattened nearly as muchas the central ortions. After the end of the sheath 10 has een cut back,'the upper and lower sides of the sheaths of the heating units. 11 and 12 are cut 01f at 13 and 13 (Fig. 6) flush with the surfaces of the portions of these sheaths in the sheath 10. This does not quite cut through the walls of the sheaths of the heating units 11 and 12 and is necessary to permit the cap 17 to he slipped over the projecting ends of the sheaths 11 and 12. The cap 17 is then put in place and secured by making the brazed joint 18 between the cap and the sheath 10. The outer end of the heating vunits provided with the terminals 19 and 20 are spread apart somewhat to give better electrical clearance.

On the outer end of the heater is a protecting casing or head enclosing the. terminals. This head comprises a flange 21 which is secured to the outer end of the sheath 10 by means of a brazed joint 21, and is threaded to receive a short length of pipe 22. The outer end of the pipe is closed by a cap 23. An electrically insulating bushing at is secured in the cap 23 by nu-ans of a snap. ring 25, and the insulated conductors .26 and 27 leading from a suitable source of electrical supply are led through this-bushing and electrically secured to the terminals l9 and 20 respectively. The terminals and barcd ends of the conductor are insulated by a wrapping lt will be understood that the connections between the conductors 26 and 27 and the terminals are made and the tape 28 wound on before the pipe 22 and head 23 are secured to the flange .21.

Obviously more than two sheathed wire heating units may he prm'idcd in the sheath 10. For example. four heating units. 29. 30. 31 and 32 may be provided, as shown in Fig. 8, in whichcase each unit is compressed so that its cross-section has. substantially the shape of a quadrant.

While we have described our invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that we do not limit our invention thereto, since various modifications thereof will suggest themselves to those skilled inthe art without departing from the spirit of our invention, the scope ,of whichis set forth in the annexed claims.

' What we claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of making an electric heater which consists in placing a plurality of cylindrical sheathed wire heating units lengthwise in a metallic sheath, and then reducing the cross-section of said sheath until said heating units are compressed together so as to substantially fill said sheath.

" 2. The method of making an electric heater which consists in providing a tubnlansheath,

slightly flattening said sheath, placing a plurality of round sheathed wire heating units lengthwise in said flattened sheath, and then reducing the sheath'and heating units until said sheath has ,a. substantially round crosssection and said heating units are compressed together into a substantially circular crossseetion. v

3. The method of making an electric heater which consists in providing a tubular sheath, counterbori'ng the ends of said sheath, slightly flattening said sheath, placing a plurality of round sheathed wire heating units lengthwise in said flattened sheath, reducing the sheath and heating units until said sheath has asubstantially round crosssection and said heating units are compressed together into a substantially circular cross-section, cutting off the counterbored portion of one end of said sheath. connecting said heating units together at said end, and then securing a cap over said end of the sheath.

4.. An electric heater comprising an outer metallic sheath. a plurality of heating units in said sheath each being provided with a metallic sheath. said units being arranged in lengthwise engagement with each other and ha ring a combined cross section substantially lilling said outer sheath.

5. .-\u electric heating unit comprising a cylindrical metallic sheath, a plurality of individually sheathed heating units extending side by side lengthwise ofsaid sheath and secured tightly therein.-said units having complemcntaiy cross sectional shapes substantially filling said outer sheath.

6. The combination with a plurality of heating units each com risin a metallic,

sheath, a resistance-heating element in said sheath and heat refractory insulating material surrounding said element, of an outer inetallic sheath surrounding said units so as to secure them together, said units having complementary shapes substantially filling said outer sheath.

7. An electric heater comprising a metallic sheath, a lurality of heating units in said sheath each eing provided with a metallic sheath, said units being arranged in lengthwise engagement with each other and being provided with a combined cross section substantially filling said sheath, an electrical connection between said units at one end, terminals for the other ends of said units projecting from said sheath, and a head member secured to said sheath enclosing said termi nals.

8. The method of making an electric heater wherein are used an outer metallic sheath and a plurality of heating units each comprising a resistance conductor embedded in insulating material in a metallic sheath, which consists in placing the heating units lengthwise in the outer sheath and then reducing the cross-section of the outer sheath until said heating units are compressed together into complementary shapes substantially filling the outer sheath.

In Withness whereof, we have hereunto set our hands this 10th day of July, 1925.

CHARLES C. ABBOTT. ARTHUR E. HUNT. 

